1. Field of the Invention
The invention refers to a device for monitoring the distance of the front surfaces of rails, for example in connection with expansion junctions or supporting structures, in which the rails are subjected to multi-axial load.
2. Description of the Prior Art
Rails and tracks are, as a rule, mounted on a sub-structure, for example on sleepers. In a route of tracks it is sometimes necessary to provide expansion junctions to allow shifting movement of the rails in their longitudinal direction without any deformation of the rails in a transverse direction relative to their longitudinal direction. In case of such rail junctions, the rails are, under the proviso of a correspondingly stable substructure, subjected only to shifting movement in their longitudinal direction, so that it is easily possible to exactly measure the mutual distance of the rails within the area of expansion junctions.
Tracks that are arranged on substructures and that are multi-axially stressed can not be supervised easily with conventional measuring equipment. It is in particular in connection with tracks mounted on bridges or mounted in floor constructions, that there may occur, in addition to possible shifting movement of the rails in longitudinal direction of the rails, deviations in a transverse direction relative to the longitudinal direction of the rails; the deviations being determined in a suitable manner. However, such additional movements of the substructure detract, considerably from the accuracy of measurement independent from determining additional deviations. Particularly in cases of analogously determining the distance by means of inductive proximity sensors, any swivelling movement of rails would result in an inclination of the measuring surface relative to the sensor, causing indication errors and not allowing exact measurements to be made. It is just in cases of bridges and where rails are supported in a more or less floating manner that it is of substantial importance to exactly determine the exact length of the expansion junctions independent from any additionally determined deviations, to thereby be in the position to correctly supervise the operational safety of the track being travelled.